This proposal is a competitive renewal for Ohio State University?s participation in the Cooperative Multicenter Maternal-Fetal Medicine Units Network. The purpose of the Network is to investigate problems in clinical obstetrics, particularly those related to prevention of low birth weight, prematurity, and medical problems of pregnancy. The investigators have been a member of the MFMU Network for the past eight years. In this proposal they have described the academic productivity of the members of their research team specifically during the past four years in the Network, but also major accomplishments during the preceding four years. The investigators have also provided current information about their population and facilities. For their concept, they propose a prospective randomized trial of medication and bed rest versus placebo in women who have a history of preterm birth, a positive fibronectin, and a cervical length less than 35 mm at 22-24 weeks. The primary hypothesis is that treatment with bed rest and medication will reduce the rate of recurrent preterm birth by 50% compared with placebo, medication and no bed rest in this group of women. The investigators are committed to working cooperatively with Network staff and member units in identifying priority issues for research, developing and implementing protocols, collecting and transmitting quality data in a timely manner, and analyzing and publishing results of MFMU trials.